On Fri, Feb 4, 2022 at 7:34 PM Tomasz Rola <[email protected]> wrote: > > > > > > > > *from the point of view of Earth-based observer, planets are just another > light points on the night sky, only moving strangely. Such an observer has > no way to say if, for example, Mars is really different, or even a planet, > or if it is maybe some star which looks for a place to stick and stop > forever. Only with telescope one can see that Mars is a disc, and disc > changes with time, but periodically, etc etc. But objective observer has no > way to say that Mars is a planet based on merely naked eye observations,*
That is not true, even the ancient Egyptian's knew there was something special about Mercury, Venus, Mars, Jupiter and Saturn. Johannes Kepler didn't know the planets could be resolved into discs and he didn't need to know that to derive his 3 laws of planetary motion, and a computer wouldn't need to know that either. Kepler didn't have a telescope but he did have Tycho Brahe's excellent naked eye measurement of the movements of the planets over many decades, especially detailed were those of Mars. Kepler knew that the planets moved in a complicated path relative to the fixed stars and then after a fixed amount of time that was different for each planet the path repeated. Kepler spent years developing a very complicated earth centered model with lots of epicycles that fit Tyco's data pretty well, and a lesser scientist might've been satisfied with that but Kepler was not. Kepler knew Tyco's data was very good and the discrepancy between theory and observation was just too large to ignore, so reluctantly he junked years of work and went back to square one. After more years of work he found a sun centered model and his three laws and that fit Tyco's data almost exactly and was much simpler. John K Clark See what's on my new list at Extropolis <https://groups.google.com/g/extropolis> tbk -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv37XKNGmfX%2BV5X3%3DXJebx48yo3D6dU0dr%2B5_LC5YAy6OQ%40mail.gmail.com.
